型態特徵

Deciduous trees or shrubs; bark smooth, gray; winter buds conspicuous, acute, with many imbricate scales. Leaves somewhat 2-ranked, serrate, plicate, 7–24-penninerved, often cordate. Staminate catkins pendulous, enclosed in buds during the winter, sessile near the ends of short lateral branches; flowers solitary in axil of each bract, without calyx, stamens 3–13, filaments 2-forked. Pistillate spikes terminal on leafy branches, erect, each bract bearing 2 flowers; calyx limb minute, superior, 6–10-dentate; ovary 2-celled, each cell 1-ovuled; style arms 2, long stigmatose on inner surface. Nuts ovoid, acute, subtended at base by a 3-lobed or dentate elongate foliaceous bract and bracteoles, 1-seeded.